title: Mammary tumours in Sprague-Dawley rats after initiation with DMBA followed by exposure to 50 Hz electromagnetic fields in a promotional scheme.
abstract: In order to test whether a transient-producing intermittent magnetic field (MF) acts as a promoter in rat mammary tumour development, a study of a 50 Hz sinusoidal MF with flux densities of 0.25 and 0.5 mT was performed on female Sprague-Dawley rats. A single administration of 7 mg of 7,12-dimethyl-benz[a]anthracene (DMBA) was given by gavage to 52-day-old animals. After 1 week, exposure to an intermittent (15 s on/15 s off) transient-associated magnetic field was started. MF exposure was performed for 19 or 21 h per day up to 25 weeks, when the study was terminated. Twice a week a careful examination with palpation for tumours was done. Tumour incidence, the number of tumours per animal, tumour volume and tumour weight were recorded. A total of 70% of MF-exposed animals developed tumours. For animals exposed to DMBA alone the correspondent figure was 71.7%. No statistical differences were seen either for tumour-bearing animals or for the total number of tumours. A slightly larger total tumour weight and tumour volume was seen for animals exposed to 0.25 mT MF. These differences were not statistically significant.
authors.affiliation: Department of Toxicology and Chemistry, National Institute for Working Life, Solna, Sweden.
authors.forename: T
authors.initials: T
authors.lastname: Ekström
authors.forename: K H
authors.initials: KH
authors.lastname: Mild
authors.forename: B
authors.initials: B
authors.lastname: Holmberg
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene; D000818:Animals; D002273:Carcinogens; D004307:Dose-Response Relationship, Radiation; D004574:Electromagnetic Fields; D005260:Female; D008325:Mammary Neoplasms, Experimental / Q000209:etiology*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D002273:Carcinogens; D015127:9,10-Dimethyl-1,2-benzanthracene